The planet’s corals are currently experiencing the most massive bleaching episode ever recorded due to high ocean temperatures, a US government agency warned on Friday.
The phenomenon linked to climate change, which threatens the survival of reefs rich in biodiversity, now affects more than two thirds of corals in the Atlantic, Pacific and Indian Ocean.
“The planet is currently in the midst of the most massive bleaching episode ever recorded,” Derek Manzello, coordinator of the coral program at the National Oceanic and Atmospheric Administration (NOAA) told AFP. ).
The episode, which is still progressing, is the fourth since 1998.
“Between January 1, 2023 and October 10, 2024, approximately 77% of the world’s coral reefs experienced thermal stress at levels consistent with bleaching,” he added by email. “This percentage is still increasing.”
The unusual heat stresses the corals, which expel their zooxanthellae — algae living in symbiosis with them which provide them with the nutrients they need. Deprived of these algae, the coral loses its color and risks dying.
After two episodes in 1998 and 2010, the previous record was recorded between 2014 and 2017, during which 65.7% of the planet’s coral reefs were affected. “So we surpassed the previous record of 11.3% in half the time. This percentage is still growing,” added Derek Manzello.
NOAA has obtained confirmed reports of bleaching events in 74 countries or territories in the Northern and Southern hemispheres.
Around 850 million people worldwide depend on coral reefs for work and food. Reefs, which are home to very rich and diverse ecosystems, also protect coasts from storms and erosion, according to the NGO WWF.
The rate of ocean warming has almost doubled since 2005, according to a report from the European Copernicus observatory published at the end of September. This phenomenon is accompanied by an increase in marine heatwaves. Thus, 22% of the world’s oceans experienced at least one severe or extreme heat wave in 2023.
This warming is explained by the fact that the oceans have absorbed “more than 90% of the excess heat of the climate system” since 1970, caused by humanity’s massive emissions of greenhouse gases, according to the IPCC. .
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